FIG. 1 illustrates a schematic diagram of a prior-art machine for blasting abrasives that is used for shot blasting.
The machine for blasting abrasives comprises a nozzle (a nozzle for shooting) 113 for shooting abrasives onto a work, a jig 115 for holding the work, and a door 119 for opening and closing a gateway 117 to bring the work to be processed in and take the processed work out. The height of the jig 115 is adjustable so as to keep the work W in a position to face the nozzle 113. The jig 115 is attached to a vertically-moving pivoting table 116. Auxiliary cylinders 131 for clamping, which are disposed at the respective four corners of the door 119, enable the door 119 to tightly contact, and separate from, a surrounding sealing material 121, which is disposed along the outer rim of the gateway 117. This structure is designed to withstand a vacuum or an unexpected high pressure in a chamber for processing.
The door 119 is disposed outside a sidewall 111b of the chamber 111. The door 119 slides vertically or laterally (vertically in FIG. 1) along the outside of the wall by means of a cylinder 123 for opening and closing the door. See Paragraph 0002 of Japanese Patent Laid-open Publication No. 2000-6028 and FIG. 1 of Japanese Patent Laid-open Publication No. H6-771.
However, the above door has the following problems. Reference is now made to Paragraph 0002 of Japanese Patent Laid-open Publication No. 2000-6028.
“The scattered blasting materials or dust generated by processing easily adhere to the surface of the door facing the machine for shot blasting. Thus the blasting materials on the surface of the door may slide into the sealing surface to deteriorate the seal. They may fall out of the machine, to contaminate the area near the machine. These have been problems. Further, the machine for shot blasting is normally kept in a vacuum during the process to prevent the shot-blasting materials from flowing out. Thus if the door is opened during the process, a differential pressure is applied to the door. That causes a problem in the operability of the door.”
To solve the problems, a device for a door for a work in a chamber for shot blasting is proposed by the prior-art publication Japanese Patent Laid-open Publication No. 2000-6028 (see claim 1).
Claim 1 says the following:
“A device for a door for a work in a chamber for shot blasting, wherein an opening for passing the work is formed in a surrounding wall of a machine for shot blasting, the machine processing the work by shooting blasting materials from a nozzle for blasting by means of a high-velocity airflow, the door being provided so that the door closes the opening by contacting the rim of the opening from the inner side of the chamber.”
The door disclosed in the publication is attached to the sidewall. It swings to open and shut. Thus, when the door is opened, blasting materials (abrasives) that have adhered near the door may fall outside the chamber. Thus the following component is proposed to effectively prevent the blasting materials from adhering to the door (see claim 3 and Paragraph 0004).
“A protecting cover is provided above the opening. Auxiliary covers are provided between the side section of the protecting cover and the periphery of the machine for shot blasting. A means for supplying air under the protecting cover is provided.”
The prior-art publication Japanese Patent Laid-open Publication No. H10-151566 discloses a machine for burring by shot blasting to solve the problem wherein shot materials fall outside the machine (see Paragraph 0010). In the machine a gateway for a work is formed in the ceiling of the machine. One swinging door is attached by a hinge to the rim of the gateway to open and close it. The door has tapered edges (see the abstract, claim 1, and FIGS. 1 and 3).
However, in the publication, the direction to bring the work into the machine is offset from the center of a jig 15 for holding a work (a means for mounting a basket) when the work is processed. Thus a mechanism to rotate the jig 15 is needed. Further, a first cylinder for opening and closing the door is needed on the upper surface of the door. A second cylinder that is mounted on the pivot of the door is also needed. The piston rod of the second cylinder is illustrated as penetrating the door. Therefore its structure is unclear. Thus no detailed description is given that is sufficient and clear so as to enable one having ordinary skill in the art to work the invention.
It is not denied that in Japanese Patent Laid-open Publication No. H6-771 there is “a door for bringing a work in and taking it out is provided on an upper wall in a chamber for grinding” (see the abstract and claim 1). However, it is not intended nor suggested to dispose a gateway for a work with a door on the upper wall to prevent abrasives from dropping outside the machine when opening or closing the door. Actually, in the embodiment, which should be preferable, a sliding door for the gateway is provided at the sidewall.
All of the prior-art publications described above relate to a machine for shot blasting, not to a machine for shot peening.
The object of shot peening is for the surface modification of a work. That of shot blasting is for burring, grinding, making a matte finish, polishing, or making a pearskin-finish or a leather-texture finish, of the surface of a work. Thus they are different processes.
For shot peening, shots with a diameter
(e.g., 20 to 100 μm)
that is smaller than that of the blasting materials have increasingly been used to enhance the effect of shot peening. The sizes of the shots for blasting are generally in the range of
50 to 2500 μm.
Hence, the structure for sealing disclosed in Japanese Patent Laid-open Publication No. H10-151566 may not cause problems when shot blasting is carried out. However, when shot peening is carried out where fine abrasives (shots) are used, the shots may penetrate the gap between the inner surface of the gateway and the opposing outer surface of the door. Thus a problem such as a bite by the abrasives may occur there. The structure for sealing is formed as follows:
“A sealing member 47 includes an elastic portion 47a that is formed with silicone covered with glass wool and an attaching member 47b that is a portion extending from the glass wool. The attaching member 47b is fixed to the sidewall of a door 40 by a fixing member, such as a screw. The elastic portion 47a is positioned at the lower edge of the sidewall of the door 40” (see Paragraph 0035 and FIG. 5).
Furthermore, the structure for sealing the door that is disclosed in Japanese Patent Laid-open Publication No. 2000-6028 and in No. H10-151566 is complicated.
In the structure for sealing disclosed in Japanese Patent Laid-open Publication No. 2000-6028 a means for supplying air is needed as described above. In the structure for sealing disclosed in Japanese Patent Laid-open Publication No. H10-151566 it comprises a link mechanism with two pin joints. To withstand a negative pressure during a process, a robust link mechanism must be used.